1. Field of the Invention
The invention relates to a drying cylinder for drying a paper, board, tissue or another fibrous web in a machine for producing and/or finishing the same, having a load bearing element and an outer cover layer which is heated by a hot fluid.
2. Description of the Related Art
Drying arrangements having drying cylinders have been known for a long time, the fibrous web wrapping around these being supported by a dryer fabric. As a result of the contact of the fibrous web with the hot circumferential surface, heating occurs and, in particular after being led away from the drying cylinder, evaporation occurs. Because of the limiting drying rate of the drying cylinders, these drying arrangements need a relatively large amount of space. The drying rate is limited substantially by the cover thickness, which is part of the thermal resistance of the drying cylinder. Due to the length of several meters and the diameter of more than one meter the drying cylinders require a relatively thick cylinder shell in order to ensure adequate stability.
What is needed in the art is a device to increase the flow of heat through the shell of a drying cylinder.